Zombified Piglins Stuck In The Nether Portal

Whenever I am close to my nether portal, zombified piglins appear rapidly and increase quickly in high numbers. When I am in the nether, the piglins do not spawn in my portal. I have tried using kill commands multiple times but the piglins keep reappearing. I check in the nether and there are not many piglins in my area, but huge amounts keep appearing in my portal, and will not leave.